Breast cancer cases diagnosed after 1994 and equal number of frequency-matched (by age within 2 years and ethnicity) controls. Cases and eligible controls with at least 3 screening mammograms since 1994 will be recruited through the University Hospitals Breast Center, and primary care clinics within the University Hospitals Health System (UHHS). The restriction of 3 or more screening mammograms will allow us to adequately model the longitudinal change patterns.